Tennessee antigen, a tumor-associated glycoprotein, with a molecular weight of 100 kilodaltons is chemically and immunochemically different from CEA. The TennaGen hemagglutination inhibition assay has been used to measure levels of Tennessee antigen in 7300 assays. Normal levels were obtained in 93% of 1090 normal individuals, 70% of active benign gastrointestinal and lung disease while 80% of 178 pulmonary carcinoma and 81% of 205 colorectal carcinoma had elevated levels; 95% of 20 colorectal patients classified as Dukes' A had elevated preoperative levels. The refinement in measurement of levels of Tennessee antigen using the enzyme immunoassay methodology will increase the marker's use in monitoring clinical courses of treatment and as a diagnostic aid. The objective of this proposal is to utilize available Tennessee antigen and antibody in developing an enzyme immunoassay and to evaluate the sensitivity and value of the marker when using a more sensitive methodology. The enzyme immunoassay allows expansion of the scale so that there is greater differentiation between a negative and positive range. The readability of the assay by electronic apparatus is more reliable and consistent than visual interpretation of the hemagglutination inhibition assay. The development of stable enzyme immunoassay reagents will result in a more economical assay kit. (2)